1. Field of the Invention
The present invention relates to a projection lens used in a video projector for projecting on a screen an enlargement of an image appearing on a cathode-ray tube (CRT), and more particularly to a high resolution projection lens applicable to a high definition video projector employing a high resolution CRT.
2. Description of the Prior Art
Conventional projection lenses as disclosed in Japanese Laid-Open patent applications Nos. 58-125007 and 59-155818 and U.S. Pat. Nos. 4,300,817 and 4,348,081 are for the CRT on which an image is formed by 525 scanning lines(resolution is 525 lines), and most of them do not provide correction for chromatic aberration. Some projection lenses which provide correction for chromatic aberration have been proposed as disclosed in the Japanese Laid-Open patent application No. 59-170812 and U.S. Pat. No. 3,888,173.
However, these conventional projection lenses have, because of large residual aberrations, a serious deficiency of performance as a projection lens for use in a high definition video projector of 1,125 scanning lines.